closes docs: remove references to Py_USING_MEMORY_DEBUGGER (GH-30284)

Misc/README.valgrind

@@ -12,12 +12,9 @@ can be used to force the usage of the malloc() allocator of the C library.
 If you don't want to read about the details of using Valgrind, there
 are still two things you must do to suppress the warnings.  First,
 you must use a suppressions file.  One is supplied in
-Misc/valgrind-python.supp.  Second, you must do one of the following:
-
-  * Uncomment Py_USING_MEMORY_DEBUGGER in Objects/obmalloc.c,
-    then rebuild Python
-  * Uncomment the lines in Misc/valgrind-python.supp that
-    suppress the warnings for PyObject_Free and PyObject_Realloc
+Misc/valgrind-python.supp.  Second, you must uncomment the lines in 
+Misc/valgrind-python.supp that suppress the warnings for PyObject_Free and
+PyObject_Realloc.
 
 If you want to use Valgrind more effectively and catch even more
 memory leaks, you will need to configure python --without-pymalloc.